S820E Microwave Site Master™ User Guide : Measurement Review : Measurement Overview : Calibration
 
Calibration
For accurate results, the instrument must be calibrated before making any measurements.
The Cable and Antenna Analyzer mode requires calibration standards or external sensors, which are sold separately.
The instrument must be re‑calibrated whenever the temperature exceeds the calibration temperature range window or whenever the test port extension cable is removed or replaced. The instrument must also be re‑calibrated every time the setup frequency changes. Refer to Calibration, CAA for details on how to perform a calibration and the various calibration options available for coaxial cable and waveguide measurements.
Note 
Anritsu recommends allowing the S820E to warm up for at least 10 minutes to typical operation temperature before calibrating. The instrument will require a new calibration if the internal instrument temperature changes more than ±10 ºC after calibration.
The external InstaCal Calibration Module is NOT compatible with the Microwave Site Master S820E.